Helmets used to provide head protection may be worn in a variety of environments and for a variety of purposes, such as for protection against ballistic threats. Helmets that protect against ballistic threats may be formed from layers of woven or linear fibrous materials that are combined with a matrix material and formed into a hemispherical shape. The matrix material bonds with the fibrous materials to form a rigid outer shell for the helmet. Either as part of the forming operation, or once the forming is complete, the excess material on the edge of the helmet is typically trimmed to provide the final shape of the helmet, and an edge band is applied to finish and protect the exposed fibers along the edge of the helmet. The final trimmed shell is usually fitted with liner and retention components to secure the helmet to the wearer's head by means of a flexible chin strap.
The edge band is typically channel shaped and made of a conformal material (e.g. rubber) which is flexible enough to be wrapped around the edge of the helmet when applied by hand using an adhesive to bond it in place. The flexible material of the edge band seals and protects the fibers on the edge of the helmet, preventing entry of moisture or other hazards which might degrade the materials. However, this edge band is not a structural element and does not provide additional strength and/or rigidity to the helmet or improve the ballistic performance of the helmet.
Recent advances in technology resulting from new fiber and matrix materials, as well as new processing techniques, may provide greater performance against ballistic threats, for example by providing the same level of protection at a lighter weight, or providing an increased level of protection at the same weight. This improved performance is partly due to the increased strength of the composite recipe, which can withstand more energy before breaking than previously utilized materials. This results, at least in part, from the ability of these composites to stretch without allowing threats to penetrate and pass through. However, this inherent flexibility is disadvantageous to other performance requirements of the helmet that require a more rigid structure, for example to reduce backface deformation of the shell when struck by ballistic threats, and to dissipate blunt trauma impacts over a larger surface area and provide protection from crushing loads.